Because of their high water content, mouthwashes present particular challenges in preventing microbial contamination. Arginine and other basic amino acids have been proposed for use in oral care and are believed to have significant benefits in combating cavity formation and tooth sensitivity, but formulation in a mouthwash presents special challenges as mouthwashes comprising arginine or basic amino acids tend to have a basic pH, increasing potential for microbial contamination compared to acidic formulations. Moreover, not all preservatives are active at higher pH. Some preservatives negatively affect the taste or aesthetics of the product. While certain preservatives, such as ethanol or parabens, are known to effective at a range of pHs, these preservatives are not suitable for all products or all markets.
Accordingly, there is a need for improved preservative agents for use in mouthwashes comprising basic amino acids.